1. Technical Field
This invention relates to gearshift mechanisms and, more particularly, to an in-line gearshift mechanism for controlling the directional mode of operation and gear selection of a powershift transmission of an agricultural vehicle.
2. Discussion
Gearshift mechanisms are used in a wide variety of applications to allow an operator to control a transmission of a vehicle so as to select not only a directional mode of operation of the vehicle, but a specific gear in which the transmission of the vehicle is to be operated.
Traditionally, heretofore developed gearshift mechanisms have usually required shifting to be performed in an "H" pattern, or some variation thereof. Accordingly, when shifting from, for example, first forward gear to, for example, third forward gear, the operator is required to not only move the gearshift lever linearly but also perpendicularly for a brief period of travel, and then typically linearly again. Accordingly, many shifts between gears, or between directional modes of operation, require the operator to move the gearshift lever in two or three distinct directions. Even with direction "reverser" transmissions, where levers are moved generally in a straight path, multiple levers are required to accomplish multiple gear selection.
In many applications, particularly agricultural and off-road earth moving applications, frequent shifting is required by the operator. The multiple, distinct movements required by the traditional gearshift mechanisms can often add significantly to the fatigue of the operator over the course of several hours of operation of the vehicle. The requirement of moving the gearshift lever in several distinct directions to accomplish a gearshift is further more apt to cause the operator to unintentionally select an unwanted gear, which may in turn needlessly stress or damage the transmission and/or engine of the vehicle. Thus, there exists a definite need to provide a gear shift mechanism which provides shifting action (i.e., shift lever movement) in logical directions to accomplish directional mode changes, as well as upshifts and downshifts, all with a single gearshift lever and with in-line shift movements.
Accordingly, it is a principal object of the present invention to provide a gearshift mechanism which allows "in-line" shifting between forward, neutral and reverse modes of operation, as well as in-line shifting between all of the forward and all of the reverse gears of a powershift transmission.
It is still another object of the present invention to provide a gearshift mechanism having a gearshift lever which accomplishes upshifting or downshifting while in a forward mode of operation with only a relatively short "in-line", linear movement towards a forward upshift or a forward downshift position, and which similarly allows upshifting or downshifting while in the reverse mode of operation by simply moving the gearshift lever linearly, in an in-line fashion, momentarily to either a reverse upshift position or a reverse downshift position.
It is yet another object of the present invention to provide an in-line gearshift mechanism having a shift lever capable of shifting between a forward, a neutral and a reverse mode of operation in in-line fashion, and further for upshifting or downshifting while in the forward mode of operation in in-line fashion, and further where the gearshift mechanism includes means operably associated therewith for determining if in fact a downshift was desired by the operator when the gearshift lever moves through the forward downshift position, and whether in fact a reverse downshift was desired by the operator when the gearshift lever is moved through the reverse downshift position.
It is further an object of the present invention to provide a gearshift mechanism for accomplishing shifts between reverse, neutral and forward directional modes of operation, as well as upshifts and downshifts in each of the forward and reverse directional modes of operation, all in an in-line fashion with no perpendicular movement of the gearshift lever, and which further includes a throttle lever for allowing an operator to adjust an engine speed of the vehicle.
It is yet another object of the present invention to provide an in-line gearshift mechanism which may be easily and conveniently assembled as an integral unit to a frame portion of the vehicle.